The Upper Permian Bellerophon Fm of the Dolomites (northern Italy) is an overall transgressive succession, which consists of a lower sulphate-evaporite unit, deposited in a barren basin, and an upper shallow-marine carbonate unit, deposited along a low-energy ramp setting. This succession, mainly Changhsingian in age, contains rich fossil assemblages, which have been studied since 19th century. Although some taxonomical groups have been object of recent revisions (e.g. nautiloids and brachiopods), the stratigraphic and systematic knowledge of the bivalves is not supported by recent studies, which are necessary to evaluate the survival rates after the end-Permian mass extinction. In this study, the biodiversity and stratigraphic distribution of the bivalves occurring in the Bellerophon Fm of western Dolomites is investigated with the aim to define the extinction patterns through the comparison with the taxa occurring in the Lower Triassic Werfen Fm. The specimens have been collected bed-by-bed from the Val Gardena and Val Badia sections aligned along a south west-north east transect, which records a slight deepening of the marine environment. Systematic assessment, based both on newly collected material and on historical collections analysis, has revealed 18 genera with 24 species. The studied material has been ascribed to the genera: Bakevellia, Chaenomya, Cosmetodon, Dyasmya, Edmonia, Eumorphotis, Palaeolima,?Palaeonelio, Permophorus, Pernopecten, ?Pleurophorella, ?Promytilus, Schizodus, Solemya (Janeia), ?Tambanella, Towapteria, Volsellina and Aviculopectinidae gen. nov. Infaunal suspension and detritus feeders suffered extinction rates higher than the semi-infaunal and epifaunal suspension feeders. The studied bivalves show a richness drop at genus level lower than other marine taxa. This higher survivorship can be related to the adaptation of the Upper Permian bivalves towards very shallow and stressed (e.g., high temperatures and low oxygen levels) marine environments, which characterized the western Dolomites during the deposition of the Bellerophon Fm
Upper Permian bivalves from the Bellerophon Formation (Dolomites, northern Italy) and biodiversity drop related to the end-Permian mass extinction
Posenato R.
2018
Abstract
The Upper Permian Bellerophon Fm of the Dolomites (northern Italy) is an overall transgressive succession, which consists of a lower sulphate-evaporite unit, deposited in a barren basin, and an upper shallow-marine carbonate unit, deposited along a low-energy ramp setting. This succession, mainly Changhsingian in age, contains rich fossil assemblages, which have been studied since 19th century. Although some taxonomical groups have been object of recent revisions (e.g. nautiloids and brachiopods), the stratigraphic and systematic knowledge of the bivalves is not supported by recent studies, which are necessary to evaluate the survival rates after the end-Permian mass extinction. In this study, the biodiversity and stratigraphic distribution of the bivalves occurring in the Bellerophon Fm of western Dolomites is investigated with the aim to define the extinction patterns through the comparison with the taxa occurring in the Lower Triassic Werfen Fm. The specimens have been collected bed-by-bed from the Val Gardena and Val Badia sections aligned along a south west-north east transect, which records a slight deepening of the marine environment. Systematic assessment, based both on newly collected material and on historical collections analysis, has revealed 18 genera with 24 species. The studied material has been ascribed to the genera: Bakevellia, Chaenomya, Cosmetodon, Dyasmya, Edmonia, Eumorphotis, Palaeolima,?Palaeonelio, Permophorus, Pernopecten, ?Pleurophorella, ?Promytilus, Schizodus, Solemya (Janeia), ?Tambanella, Towapteria, Volsellina and Aviculopectinidae gen. nov. Infaunal suspension and detritus feeders suffered extinction rates higher than the semi-infaunal and epifaunal suspension feeders. The studied bivalves show a richness drop at genus level lower than other marine taxa. This higher survivorship can be related to the adaptation of the Upper Permian bivalves towards very shallow and stressed (e.g., high temperatures and low oxygen levels) marine environments, which characterized the western Dolomites during the deposition of the Bellerophon FmI documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
